Tandem axle spring suspension system



s. G. JoHNsoN Erm. 2,686,061

TANDEM AXLE SPRING SUSPENSION SYSTEM 2 Sheets-Shea?l l Aug. 10, 1954 Filed sept. 29, 195o 2 Sheets-Sheet 2 S. G. JOHNSON ETAL TANDEM AXLE SPRING SUSPENSION SYSTEM Aug. 10, 1954 Filed Sept. 29, 1950 Patented Aug. 10, 1954 TANDEM AXLE SPRING SUSPENSION SYSTEM Samuel G. Johnson and Joseph A. Hausmann, Fort Wayne, Ind., assgnors to International Harvester Company, a corporation of New Jersey Application September 29, 1950, Serial No. 187,498

Claims.

The present invention relates to automotive vehicles and more particularly to a new and improved axle suspension system for tandem axle vehicles.

The primary objective of the present invention is to provide an extremely rugged and durably tandem axle suspension system which has relatively few parts so as to be more quickly and easily assembled and disassembled and less expensive to manufacture than axle suspension systems heretofore known.

A further object is the provision of an axle suspension system in which each axle end is provided with a novel dilferential load-receiving member for receiving predetermined portions of the frame load from a primary and a secondary load-transmitting member.

Another object is the provision of a resilient secondary load-transmitting member for dividing the frame load received thereby equally to the differential load-receiving members associated therewith.

Still another object is to provide an axle suspension system in which the frame load is transmitted to the axles from a plurality of spaced points along the frame, thus distributing the load over a greater area and permitting the use of tapered frame side members or sills.

A still further object is the employment of rubber bushings at all bearing points to effectively allow a limited torsional movement and twisting action between the parts and, at the same time, to eliminate the need for lubrication of the bearing surfaces.

A further object is the provision of an axle suspension system in which the force component of the frame load transmitted through the spring means is greatly decreased in comparison with prior suspension systems to thus allow the utilization of a much lighter spring for a given maximum frame load. In other words, only a portion of the frame load is transmitted to the axles through the medium of the spring means.

The foregoing and other important objects and desirable features inherent in and encompassed by the invention, together with many of the purposes and uses thereof, will become readily apparent from a reading of the ensuing description in conjunction with the annexed drawings, in which:

Figure 1 is a side elevational view of the rear end of the vehicle frame showing the new and improved tandem axle suspension system;

Figure 2 is a plan view of the axle suspension .system taken substantially along line 2---2 of Figure 1 with the differential load-receiving members associated with the rearward axle removed for the sake of clarity of illustration;

Figure 3 is a detailed view taken substantially along line 3-3 of Figure 1;

Figure 4 is an enlarged, fragmentary vieW taken substantially along line 4 4 of Figure 1; and

Figure 5 is an enlarged, fragmentary view taken substantially along line 5 5 of Figure 1.

Referring to the drawings, in which like reference characters designate like elements throughout the various views, there is shown the rearward portion of a longitudinal chassis or frame I0 comprising a pair of transversely spaced side sill members Il and I2 which are rigidly interconnected by a pair of longitudinally spaced cross members I3 and I4. The frame Il is carried on a spring suspension system including a pair of transversely extending parallel supporting axles I5 and I6 which in turn are supported by a plurality of ground engaging wheels II and I8, there being two pairs of wheels Il for the axle I5 and another set I8 for the axle I6. Wheels Il are shown to be the driving wheels. However, it is to be understood that the rear axle I6 as well as the forward axle I5 may function as a drive axle by the incorporation of suitable power transmission mechanism therein.L Inother words the suspension system to be described is adaptable for vehicles having two driven or dead axles, or one of each.

In the following description, only one side oi the rear portion of the vehicle will be described inv detail but it should be understood that the structure described will also appear at the opposite side of the vehicle.

Fastened rigidly to the web portion of each rsill member Il and I'2 midway between the axles I5 and It are supporting plates I9 and 20. Each plate IQ and 2o is provided with an inwardly projecting cylindrical section 2| which rigidly supports the ends of a transverse hollow tube 22. Referring specifically to the structure disposed along side sill member II it will be noted 'that an aperture 23, aligned transversely with the hollow interior of tube 22, is formed in the web portion of the sill member I I.' A supporting pin 24 has one endv inserted through aperture 23 into tube 22 and is rigidly secured thereto. The opposite end of the pin 24 projects outwardly of the sill member II and constitutes the vsupporting means for the spring structure to be described hereinafter.

4 `A leaf spring assembly or ysecondary resilient load-transmitting member, designated generally by numeral 25, is made up of a plurality of leaves 26 of various lengths which are mounted on a saddle 21. The leaves25 of the assembly are clamped in assembled relation to the saddle 21 midway between their ends by means or" inverted U-shaped bolts 2S which surround the spring assembly 25 and whose free ends extend through the saddle flanges and are secured thereto by the nuts 29. The saddle 21 in its assembled condition provides a. transversely extending bearing 35 which surrounds the outwardly projecting portion of the pin 24. Interposed between the outer surface of the pin 24 and the inner surface of the bearing 35 is a bushingl 3| of elastic ilowable material such as rubber. is nonslidably mounted on the pin and has a metal sleeve 32 secured on its outer surface. The sleeve 32 rigidly engages the interior surface of the bearing 33. It is obvious that the leaf spring assembly 25 is capable of rocking about a transverse horizontal axis corresponding to the longitudinal axis of the pin 24. The utilization of the rubber bushing 3l as described eiectively decreases vibration between the spring assembly 25 and the pin 25, and provides a pivotal cormection between the parts which does not require external lubrication.

Axle brackets 33 are xedly mounted by means of inverted U-bolts 35 and nuts 35 -on pads 311 of a conventional type formed adjacent the ends of the axles l and I5. As best shown in Fig. l, each axle bracket has an upwardly extending arm 31 and a horizontally extending arm 38. Referring to Fig, 4, it will be noted rthat the free end of the upwardly extending arm 31 rigidly carries one end 35 of a short, transversely extending 'pivot pin 4l). The opposite end IBI of the pin Bil is provided with a rubber bushing 42 similar to bushing 3l associated with pin '24.

Rigidly secured to the sill'member I I forwardly of the axle I5 is bracket i3 having a downwardly depending portion it provided with a transversely extending bearing '45. The horizontally extending arm 38 of each axle bracket 33 has a horizontal, transversely extending aperture therethrough Vfor receiving a pin '46. A bushing A1 of rubber or like material is secured to the pin 46 and is substantially enclosed by ametal sleevelike retainer, the outer surface of which rigidly engages the bearing surface formed bythe aperture extending through the arm 38. It is evident that pin 46 may rotate to a limited extent in the aperture -because of the elasticity 'of the rubber bushing 41. Asimilar pin 48 is rotatably connected to bearing 45 by means of a rubber bushing 49 and a metal retainer 50 having a channel-shaped cross section, as best shown in Fig. 3. Interconnecting thepins 46 and 58 is a torque arm 5i which includes a pair of parallel links 52, 53 having their ends rigidly connected to pins' and 48. A bracket 54, similarto bracket 43, is rigidly connected to the sill member II rearwardly of axle I6. Bracket 54 and the axle bracket 33 associated with axle I5 are interconnected by means of `exactly the same structure utilized for connecting bracket 43 and the axle bracket 33 associated with axle I5 and, hence, will not 'be described indetail. It will be -appreciated from the foregoing 'description that the driving and braking forces are effectively taken by the torque arms 5I and furthermorethe rubber bushings allow a limited torsional movement and twisting action between the parts generally caused4 when the wheels on one side'of the frame The bushing 3| y only pass over an irregularity in the terrain. It is also evident that the use of these bushings at all bearing points eliminates the need for lubrication inasmuch as relative rotational movement between the parts entails no frictional sliding of one metal part of another'metal part.

Rigidly `connected to the frame I5 adjacent each bracket 43 and 55 is a primary load-transmitting member 55. Brackets 55 have a bearing surface 55 formed therein for rotatably receiving one end of pivot pins 51. The endl received by the bearing surface is provided with a rubber bushing 58 encircled by a metal sleeve 59 which rigidly engages the `Vbearing surface 55. The pins v51 Iproject outwardly through the sill member II,

as shown in Fig. 3.

A metal sleeve 60 is non-rotatively mounted on the rubber bushing d2 associated with pin 40. A differential load-receiving beam 6I is non-rotatively mounted intermediate its ends 52, 63 upon each metal sleeve Eil. The Vbeam E! is capable of rocking about pin 'del because of the elasticity of the rubber bushing t2 interposed between the parts. One end 62 of each beam 6I is keyed or otherwise rigidly secured to the outwardly -projecting portion of each pivot pin 51, as shown in Fig. A3 of the drawings. The opposite ends 63 extend longitudinally toward the supporting pin 2:1 and have rounded abutment heads 64 which slidingly engage respectively the underside of opposite end portions of the lowermost leaf 2t of `the spring assembly 25. It will be noted, that the. longitudinal distance between pivot pin v51 and pivot pin 4B is greater than the longitudinal distance lbetween pin 45 and the center of the abutment head v5d by approximately 10% of the entire distance between pin 51 and the center of the abutment head '515. 'The signicance of this fact will be explained hereinafter.

Before describing the operation of the axle suspension system described above certain peculiarities inherent in the system will bevpointed out. The frame load force is transmitted to the supporting aides -I5 and I5 fromside sill member II from three longitudinally spaced points; namely, thev primary load-transmitting member 55 forwardly of the axle I5,*thespring assembly 25,'and the primary load-transmitting member 55 rearwardly of the axle I5. inasmuch as `these force transmitting points are spaced relatively far apart the frame load is distributed over a greater area to thus permit the use of a lighter, tapered side sill member. Furthermore, only a denite, predetermined amount of the frame load ris transmitted tothe'axles I5 and I5 by the spring assembly 25. 'The residue of the frame load is transmitted directly to the axles from the primary load-transmitting members I"55. Hence, it will thus be Obvious that va relatively lighter .spring assembly can be used as Icompared to the spring assemblies utilized in prior suspension `systems where the full vframe load vis ltransmitted from lthe frame to the axles solely by the spring assemblies.

Assuming that the wheels I-'I and 18 .are traveling over-comparatively 'smooth roads upondownward movement of the frame i0 relative to the `axles I5 and i5 the primary load-transmitting Vmembers 55 and the secondary resilient loadtransmitting member 25 move vertically toward the axles causing the differential load-receiving beams 6I to rock about pivot pins151. Inasmuch as an `intermediate.portion of each lload-receiving beaml =is pivotally supported byJone of the axles, 'it will be evident that ftheliabutment heads 64 formed on the beamsA 16:4. .opposite ith'e '.pivotzpins or spring assembly 25.

. 51 will move vertically upwardly against the yield- -able reaction force of the spring assembly 25. When this occurs torsion on the rubber bushings '42,41, 49 and 58 will be increased. Furthermore,

.the portions of frame load transferred from Vthe 'pivot pin 24 to the spring assembly 25 is equally divided between the axles by the spring assembly. In the event that the Wheels II on the axle I5 vencounter uneven terrain ahead of the wheels I8 on the axle I6, axle I5 will move vertically upwardly carrying with it the intermediate portion of the load-receiving beam 6I associated with the axle I5. Since the beam 6I is pivotally connected to the frame I upward movement of the intermediate portion of the beam I will cause the abutment head 64 formed thereon to act upwardly against the end of the leaf spring assembly 25 which it abuts and tends to rotate the saine in a clockwise direction as viewed in Figure Y1A of the drawings. Rotational movement of the spring assembly 25 will in turn cause the opposite end of the assembly to move downwardly against the abutment head 64 formed on the beam 6I associated with the rear axle I6. It will be appreciated that the reaction forces developed in the suspension system when one axle of the tan- `dem set moves relatively to the frame and the other axle are effectively distributed to both axles by the secondary resilient load-receiving member A similar reaction in reverse will occur when the forward wheels I'I level out and the rearward wheels I8 encounter the uneven spot just passed over by the wheels I'I on the axle I5.- It is therefore apparent that the wheels may'follow uneven or rough surfaces but the load will be distributed onto the respective wheels irrespective of the various positions the axle assembly may assume.

The embodiment of the invention chosen for the purposes of illustration and description herein is that preferred as the result of selective tests 1 based upon requirement for achieving the objects of the invention and developing the utility thereof in the most desirable manner, due regard being had to existing factors of economy, simplicity of "design and construction, production methods and the improvements sought to be effected. It will v be appreciated, therefore, that the particular structural and functional aspects emphasized .and a pair of longitudinally spaced, transversely disposed load supporting axles below said frame, an axle suspension system comprising a pair of longitudinally spaced frame brackets rigidly connected to said frame on one side thereof; a longitudinally disposed spring member spaced between said axles and said brackets, said spring '*member being pivotally connected to said frame `.substantially midway between its ends and being jrockableabout a horizontal axis vertically spaced p above `said axles; an axle bracket rigidly secured "connectedv -to said frame; a diiferential load-receiving member for each axle on one side of said frame; means pivotally connecting an intermediate portion of each load-receiving member to one of said upwardly extending arms for movement about a transversely extending horizontal axis, said means including a connecting element of elastic i'lowable material disposed non-slidably between said load-receiving members and said upwardly extending arms, each of said loadreceiving members extending to and having a surface slidingly engaging respectively the underside of opposite end portions of said spring member; and means including rubber in torsion pivotally connecting said load-receiving members respectively directly to said frame brackets.

2. In a vehicle having a longitudinal frame and a pair of longitudinally spaced, transversely disposed load-supporting axles below said frame, an axle suspension system comprising a pair of longitudinally spaced brackets rigidly connected to said frame on one side thereof; a leaf spring member spaced between said axles and said brackets; means for pivotally connecting said leaf springmember to said frame for rocking movement about a horizontal axis vertically spaced from said axles, said means including a rubber bushing; a diiferential load-receiving member for each axle on one side of said frame; means including a rubber bushing pivotally connecting an intermediate portion of each load-receiving member to an axle for movement about a transversely extending, horizontal axis vertically spaced above the axes of said axles, each of said load-receiving members extending to and having a surface slidingly engaging respectively the underside of opposite end portions of said leaf spring member; and means including a rubber in torsion pivotally connecting said load-receiving members respectively directly to said brackets.

3. In a vehicle having a longitudinal frame including a side sill member and a pair of longitudinally spaced transversely disposed axles below the frame, an axle suspension system for one side of said frame including said axles and frame comprising a mounting ypin projecting transversely from said sill member; a longitudinally disposed spring member; means pivotally connecting a mid portion of said spring member to said pin for rocking movement about a transverse, horizontal axis; an axle bracket rigidly secured to each axle, said brackets each having an upwardly extending arm and a horizontally extending arm; a torque arm associated with each axle, said torque arms each having one end pivotally connected to one of said horizontally extending arms and its opposite end pivotally connected to said sill member; a load-receivingbeam associated with each bracket, said beams having one end pivotally connected directly to said sill member and their opposite, free ends respectively slidably engaging opposite ends of said spring member; and means pivotally connecting an intermediate portion of eachloadreceiving beam to the upwardly extending arm 'of its associated bracket for pivotal movement about transversely extending axes.

4. In a vehicle having a longitudinal frame and a pair of longitudinally spaced, transversely disposed load-supporting axles below said frame, an axle suspension System comprising a pair of longitudinally spaced primary load-transmitting members; means for rigidly connecting said primary load-transmitting members to one side of said frame; a secondary resilient load-transmitting member spaced between said axles and said primary load-transmitting members; means l'illor spivotallyxconnecting :said 4secondary `resilient loaclatransmitting member .to said. frame for rocking movement about-.a .horizontal axis :vertically spacedvfrom said.axles,-..said means inaclu'ding a rubber bushing.; .adiilerential loadre .ceiving 1 member yfor each axle .on v4one;side -,o:l said frame; lmeans including :rubber in. torsion :pivotall-y .connecting .an 'intermediate portion'iof -each loadereceiving member lo-an axle for rocking 4movement about transversely .extending axesl vertically. .spaced from .a horizontal plane icontaining said axles, each of said load-receiving members extendingto and :having a surface slidingly engaging respectively the underside of op- .posite end portions of ysaid ,seconda-ry 'resilient 'load-.transmitting member; Aand vmeans/including yrubber in torsion pivotally connectmg said differential load-transmitting members `respectively directly to said, primary load-transmitting ,members.

.5. .Inra vehicle-having a longitudinal frame-and a-pair of longitudinally spaced, transversely dise posed load-supporting axles below said frame, an axle suspension system comprising a pair of longitudinally spaced primary load-transmittingf members on one side of said frame; means .for rigidly connecting said primary load-transmitting members to'said frame; a secondary resilient load-transmitting member spaced between said axles and said primary load-transmitting Vmem-V bers; means for pivotally connecting said secondary resilient load-transmitting member to vsaid frame for rocking movement about a horizontal axis vertically spaced from said axles; -a

differential load-receiving member for each axle.

on one side of said frame, said members being pivotally lconnected to said axles for rocking movement about transversely extending axes vertically spaced from a horizontal-plane containing Vsaid axles, each of said members extending toi., and having afsurface slidingly engaging respectively opposite end portions of said secondary re .silient load-transmitting member; and means pivotally connecting said difierential load-transmitting members respectively directly to said -ferential load-receiving member for each. axle, .said 'members Abeing pivotally supported by said axles for rocking movement about a Vtransversely extending- .axis vertically spaced from a horizontal plane lcontaining said axles, each of said members having a surfaoeslidingly engaging Irespectively oppositeiendrportions of said secondary resilient load-transmitting member; means connectingsaid differential load-receiving members respectively directly -to said .primary load-trans-f mitting members; said. secondary'resilient load- .transmitting member being capable .of .dividing the iframe load 4received thereby .equally to said differential load-receiving members.

'7. In a vehicle having a longitudinal frameandi:

apair of parallel axles transversely of. and below the frame, an axle suspension system-comprising a .longitudinally Vdisposed 4resilient .member having amid portion fpivotaily Yconnectedy to; 'saidframa said .member being adapted toatock about aztransverse, horizontal axis-spaced between 'said' axles: -a pair'ofload receiving :members reach ofzsaid members having -one zend pivotally `connected directly to said frame on one fside'thereofand an intermediate portion. pivotally connected'to :an axle, said members being .adaptedto pivot about horizontal, transversely extending axes; said .load-,receiving.members having their freeends slidingly engaging #respectively opposite ends -fof said resilient member.

6. In a vehicle having a longitudinal frame and a pairof Vparallel axles transversely of rand ,below "the frame, an `axle suspension system VVconiprising a longitudinally disposed resilientfmember having amid portion pivotally connected to said frame adapted to rock about :a transverse,

horizontal axis spaced between said axles; -..a pair .ofload-receiving members; bracket -means including rubber in torsion .pivotally `connecting oner'end of each `of the load-receiving 'members directly to said frame on one side thereof; 'means including rubber in torsion pivotally connecting anintermediate portion ci each load-receiving ymember to .an axle, Veach of said load-receiving vaxles supporting` one end of said frame; a .trunnion-on said frame spaced between said axles; qa resilient load-transmitting member having a mid portion pivoted on said -trunnion la rigid loadreceiving beam vfor each axle on one side yof said frame, each load-receiving beam having an intermediate portion pivotally connected to an axle, each yof ,said beams being adapted to vrock about a transversely extending axis, said beams having one end `pivotally connected directly to said frame and their opposite ends directly engaging respective opposite .ends of said loadtransmitting member.

,10. The combination with a vehicle frame and a pair .of axles supporting vone -end of said frame, cfa leaf spring pivotally supportedintermediate its :ends to the vehicle frame; a pair of ,rigid load-.receiving .beams .pivotally .connected directly to said frameon one/side thereof and `intermediate their ends to said axles, each `of said beams being adapted to rock about a .transversely .extending axis; said beams having their free ends .abutting respectively opposite .end portions .of said .leaf spring.

References Cited in the le o'f Vthispatent .UNITED STATES PATENTS Number Name iDate '320,707- IDowner Mayv115,-1f906 l771,488 Duesler' July29, 1930 1,940,914 '-Marcum Deer-26,1933 -2;(l80,f123 Francis May :11, 1937 2,420g843 -Shuey- May 121),.1947 "2;496A28 Avila Feb. 27,-"1'950 2,644,698 Thornton July "7, .11953 FOREIGN PATENTS Number Country Date 732,660 France `Se1:i'..'23,19.32 

